One widely-used type of precision boring apparatus comprises a rotatable boring bar, which is attached to and rotatable by, a machine tool spindle. One or more cutting blocks of a given size are connected to the free end of the boring bar, in order to be able to machine a bore of a given diameter. Thus, when it is desired to produce a bore of a different diameter, it is necessary to stop the rotation of the machine tool and to replace the or each cutting block with a different block or blocks to produce a bore of a different diameter. This is very inconvenient, since it requires the provision of a set of many different cutting blocks of different sizes, which is very costly, and which takes up much room in storage. Furthermore, the replacement of the cutting blocks must be performed by a skilled operator, in order that the new cutting block may be correctly set. The stopping of the cutting machine, the replacement of cutting blocks and the recalibration, if necessary, obviously takes a considerable amount of time, and this time is considerably increased when it is realized that for each bore, it is usually necessary to bore in a plurality of stages, usually a roughing stage, a semi-finishing stage and a finishing stage.
It is known to provide boring systems with radially-adjustable cutting blocks. The simplest versions include a manually rotatable adjustment member which screw-threadedly engages an actuating member whose subsequent displacement is used to displace a cutting block radially by means of interengaging splines and grooves on the cutting block and the actuating member, the splines and grooves being inclined to the displacement direction of the actuating member. It is believed that examples of this are shown in U.S. Pat. No. 1,684,772, GB 2,204,513 A, FR 967,093, FRI, 038,110, DE 813,919, DE 3,245,195 A1 and DE 2,012,643. A similar arrangement is shown in GB 2,131,332 A, but wherein the adjustment is effected automatically, for example by means of a stepping motor.
However, these devices all suffer from two major disadvantages. Firstly, the adjustment of the cutting diameter can only be effected when the tool is stationary, this making it impossible to produce gradually varying "profiled" bores such as tapered bores. Secondly, and more significantly, each arrangement is only able to produce bores over a given cutting diameter range. In order to produce bores of a diameter outside that range, it is necessary to fit a different cutting block, which necessitates a complicated and time consuming dismantling and subsequent reassembly and recalibration of the cutting apparatus.
It has been found possible to overcome the first of the aforementioned disadvantages by providing an actuating member which is slidably disposed in a mounting tube which also slidably receives the or each cutting block in a groove formed therein. One example is disclosed in DE 2,025,006 A, and it is believed that DE 1,028,853 discloses other examples.
Although the devices can produce profiled bores, each cutting block is still able only to produce bores over a given range of diameters, and time-consuming and skilled dismantling of the assembly is necessary in order to replace one cutting block with another of a different cutting range. This is only made more difficult by the mount of the actuating member within the mounting tube.
U.S. Pat. No. 4,508,475 also discloses a similar actuating mechanism, but the mechanism merely withdraws a grooving tool to an inoperative position and extends it to an operative position when desired. However, the same disadvantages are present with this device.
It is an object of the present invention to provide a boring apparatus which overcomes the disadvantages described above.
In accordance with the present invention there is provided a boring apparatus comprising:
an elongate support body adapted to be rotatable by a machine tool spindle;
first securing means for releasably securing said elongate support body to said machine tool spindle;
a cutter support body releasably securable to the end of said elongate support body remote from said machine tool spindle;
second securing means for releasably securing said cutter support body to said end of said elongate support body;
cutting tool guide means in said cutter support body;
a cutter tool slidably disposed in said cutter guide means are restricted by said guide means to be displaceable in an adjustment direction inclined to the rotational axis of said elongate support body as dictated by the guide means;
an adjusting member disposed within said elongate support body and being movable along an axis which is substantially coaxial with the rotational axis of said elongate support body; and
an interengaging coupling on said adjusting member and said cutter tool whereby movement of said adjusting member along its said axis of motion induces movement of said cutter tool in said adjustment direction.
Such an arrangement, with the cutter or cutters located in modular fashion to a cutter support body, allows the cutter support body and cutters to be removed from the elongate support body as a whole, and does not necessitate dismantling of the cutters. In order to be able to cut bores of a different diameter range, it is merely necessary to remove the cutter support body, housing the cutters, and to replace it with a different support body having cutters capable of boring a different range of diameters.
Preferably, the cutter guide is provided in the cutter support body, and in a preferred embodiment it is adapted to receive two cutters. The two cutters may be in slidable engagement with each other.
The cutter support body may further comprise a retaining washer which is releasably securable to the main cutter support body portion. The retaining washer may be provided with passage means for the passage of a portion of the cutter adjustment member.
In a preferred embodiment, the adjustment direction is substantially perpendicular to the rotational axis of the elongate support body.
The cutter adjustment member preferably extends out of, or is extensible out of, the elongate support body within which it is located. This greatly assists the removal and fitting of cutter support bodies and their associated cutters.
The apparatus is preferably provided with securing means for releasably connecting the cutter adjustment member to a machine tool spindle.
Preferably, retaining means are provided to retain the or each cutter in the cutter support body.
By way of example only, a specific embodiment of the present invention will now be described, with reference to the accompanying drawings, in which:
FIG. 1 is a perspective view, partly cut away, of a first embodiment of boring system in accordance with the present invention;
FIG. 2 is perspective view of the boring system of FIG. 1;
FIG. 3 is an exploded front perspective view of the cutting head assembly of the boring system of FIG. 1;
FIG. 4 is a rear perspective view of the assembled cutting head assembly of FIG. 3;
FIG. 5 is a front perspective view of the boring system of FIG. 1, with the cutting head assembly removed;
FIG. 6 is an exploded perspective view of part of the boring system of FIG. 1; and
FIG. 7 is a cross-sectional side elevation of part of the assembled cutting head of FIG. 3.